1. Field of the Invention
The present invention relates to an electrolytic cell. More particularly, it relates to an electrolytic cell having a novel structure using a cation exchange membrane for producing an alkali metal hydroxide.
2. Description of the Prior Arts
In a process for producing an alkali metal hydroxide by an electrolysis of an aqueous solution of an alkali metal chloride, a cation exchange membrane process has been widely employed instead of the conventional mercury process in view of the public pollution.
Various processes using a cation exchange membrane for producing an alkali metal hydroxide having high concentration and high purity have been proposed instead of the process using an asbestos.
On the other hand, an energy saving has been required in the world to require a lower cell voltage in such technology in view of said energy saving.
As a method of lowering the cell voltage, substances and compositions and configurations of an anode and a cathode have been studied. Moreover, compositions of the cation exchange membrane and kinds of the ion exchange groups have been studied.
These proposed processes may have certain effects. Most of them, however, have relatively low, limitations of the maximum concentration of the alkali metal hydroxide. When the concentration of the alkali metal hydroxide is over the limitation, the cell voltage is suddenly increased and the current efficiency has been lowered. Moreover, the maintenance of the low cell voltage is not satisfactory. These are not industrially satisfactory.
Recently, it has been proposed to carry out an electrolysis by using a cell wherein a gas and liquid permeable anode is brought into contact with one surface of a fluorinated cation exchange membrane and a gas and liquid permeable cathode is brought into contact with the other surface of the membrane. This process is effective for performing an electrolysis at a lower cell voltage because an electric resistance of an electrolyte solution and an electric resistance caused by bubbles of hydrogen or chlorine gas can be remarkably lowered though it has been considered to be avoidable in such field.
Such proposals, however, is still conceptional and any industrial structure of the electrolytic cell has not been proposed as the industrial apparatus for said purposes.